How to Read a Codon Chart

How to Read a Codon Chart


Captions are on! Click CC at bottom right to turn off! Ah, codons. If you chose to watch this short video, you
are perhaps searching for a little additional help to read a codon chart. And you’ve come to the right place. We’re going to assume you already have the
background from our DNA versus RNA video and our Protein Synthesis video. If not…you might want to check those out
first or otherwise jumping right into this isn’t going to make much sense. Oh, and in addition, we have a video companion
handout to this video which can be helpful. Expand this video’s details for the link
as you may want to download it first. So if you had this DNA template strand here,
you’d have this mRNA built. I know this because of how RNA bases pairs
with DNA bases. Notice how these mRNA bases are written here
in groups of 3? Each is a codon. Bases are read in threes so a codon is how
these bases will be “read.” In this example, there are a total of 5 codons. 15 individual RNA bases. By reading a codon chart, you can determine
the amino acids that will be brought in by the tRNAs. You can determine the sequence of amino acids
that make up a protein. And if you’re wondering why this matters—understanding
how amino acids are coded for helps us understand human traits and how changes in amino acids
have the potential to alter those traits. Not just for humans either but all living
organisms! The codons and their corresponding amino acids
have been discovered by scientists. There are many ways you can represent the
information in a chart. The most common ways are the rectangular codon
chart and the circular codon chart. Let’s get started. The first codon—remember codons have three
bases and codons are on the mRNA—is AUG. That means the tRNA anticodon will be UAC,
and we know that because of the base pairing rules. Now, which amino acid will that tRNA carry? Time to use the codon chart! We’ll use a rectangular one, and remember,
it’s the mRNA codon that we look at. Not the tRNA anticodon. So notice on the left side of the chart, it
is for the first base. The top is for the second base. And the right side is for the third base. We’re looking at the codon AUG. We go in order. First base letter: A. We isolate this row
here and only this row. Second base letter: U. We isolate this column here and only this
column. We’ve narrowed it down to this area here
where they intersect. Third base letter: G. Here! The codon AUG codes for the amino acid methionine. Fun fact: methionine is commonly the starting
amino acid for many polypeptide chains as AUG is a start codon. Next codon is CCA. That means the anticodon for the tRNA will
be GGU. Now, what amino acid will that tRNA carry? Time to use the codon chart! This time, we’re going to ask you to pause
the video while you try to determine which amino acid this tRNA would be carrying. Again, don’t forget to use the mRNA codon. Not the tRNA anticodon. So, in slow motion, let’s go through this
chart. First base letter: C. That narrows down this
row. Second letter C. That narrows down this column,
and therefore this area here where they meet. Third letter A. The amino acid proline! Aright, the third codon. GUC. This time, we need you to determine the tRNA
anticodon, and also, the amino acid that tRNA would be carrying. Pause the video to determine those. The anticodon, based on the base pairing rules,
would be CAG. But we use the mRNA codon for this codon chart,
and when you used it—showing this in slow motion here— you should have gotten the
amino acid valine. Now, with those three codons, we used a rectangular
codon chart. We mentioned that there are other ways to
represent the information, and the circular chart is common to find as well. The circular codon chart typically works by
starting on the inside and moving outward. So, this fourth codon we have here is UUC. That means the tRNA anticodon would be AAG,
but again we’re going to use the mRNA codon in the chart. So, we start with the center. First letter U, which isolates to this area. Then we move out one to the second letter
which isolates further: U. Finally, we move one more time to the C. This is the amino acid phenylalanine. Your turn now to use the circular codon chart
with this last codon. UAA. What does the mRNA codon UAA stand for? [PAUSE] In slow motion, you can see that we
get “stop.” This does not code for an amino acid; instead,
it is generally at the end of a sequence for a polypeptide. And, well, this signals the end of reading
the codon chart…for this little chain of amino acids anyways. In reality, polypeptides tend to have many
more amino acids than this and proteins tend to be made of one or more of these polypeptide
chains. We hope this was helpful, but before we go,
we want to mention just a few pitfalls with reading codon charts. Pitfall #1: Not using the mRNA codon. Unless it specifies otherwise, the mRNA codon
is what you want to use for the codon chart. Some students will accidentally try to use
the tRNA anticodon. Some students will try to use the original
DNA template. Now while there are charts that exist for
the tRNA anticodon or DNA, unless it specifically says otherwise, you should assume it’s for
the mRNA codon. Pitfall #2: Getting stuck on the standard
rectangular chart. Pinky has noticed students tend to have more
challenges with the rectangular one. We suggest going slowly, and even using a
highlighter if you’re able to—that way you can see where the first base isolates
the row, the second base isolates the column, and third base finishes in isolating the amino
acid. Remember to go carefully in order. Pitfall #3: Not practicing. You got to practice; that’s why this video
has a video companion. So let’s do some more practice by going
backwards! So using this circular codon chart, can you
tell me the two codons that code for lysine? Go ahead and pause the video for a moment. So, using this circular codon chart, we can
see the codons AAA and AAG code for lysine. Let’s use this rectangular codon chart here
now. Which six mRNA codons could code for the amino
acid serine? The mRNA codons that code for serine are UCU,
UCC, UCA, UCG, AGU, and AGC. Phew that’s a lot of codons! Well, that’s it for the Amoeba Sisters,
and we remind you to stay curious!

53 thoughts on “How to Read a Codon Chart”

  1. Thank you so much for uploading this video! I find your videos very helpful, and they help me so much with my homework!๐Ÿ˜‰

  2. Here is the table of contents from the video description!
    Table of Contents:

    0:15 Background Information

    0:52 Intro to Codons

    1:04 Why does learning how to read a codon chart matter?

    1:46 Example 1 (Codon 1) with rectangular codon chart

    2:57 Example 2 (Codon 2) with rectangular codon chart

    3:43 Example 3 (Codon 3) with rectangular codon chart

    4:23 Using a Circular Codon Chart with two examples

    5:38 Pitfalls to Watch Out for with Reading Codon Charts

    6:39 Working Backwards with Both Charts

    You will find the video companion to this video under the topic "codon charts" on https://www.amoebasisters.com/handouts

  3. Hey Amoeba Sisters, I just wanted to say that I've stumbled upon this channels when I was 9 and I've been watching your videos ever since. Now, 2 years later, I'm in 9th grade in Biology, and the videos are helping a lot. Thanks ๐Ÿ˜Š.

  4. ly amoeba sisters! taking physics (ib 7th) and this helped me so much last year in life science!
    also petunia, I LOVE YOUR CARTOONS!

  5. Who just watches these for fun, like on their own time, regardless of school cause theyโ€™re just that good?๐Ÿ™‹โ€โ™€๏ธ๐Ÿ™‹โ€โ™€๏ธ๐Ÿ™‹โ€โ™€๏ธ

  6. Thank you very much took bio two years ago totally forgot about this but watched it just because your guys voices are awesome!

  7. You guys inspire me to keep learning! Thanks for the help!โค๏ธ๐Ÿ’—โค๏ธ๐Ÿ’—โค๏ธ๐Ÿ’—โค๏ธ๐Ÿ’—โค๏ธ๐ŸŒธ๐Ÿฅฐ๐Ÿ˜†๐Ÿคฉ๐ŸŒŠ๐Ÿ‘๐Ÿ˜†๐ŸŒธ๐Ÿ˜†๐Ÿฅณ๐Ÿ˜†๐Ÿ˜Š๐ŸŽ๐Ÿคฉ๐ŸŒธ๐Ÿ‘‹๐ŸŒธ๐Ÿฅฐ๐Ÿ˜†๐Ÿ‘Œ๐ŸŽ๐Ÿคฉ๐ŸŒธ๐Ÿง๐ŸŽ‰๐Ÿ‘Œ๐ŸŽŠ๐Ÿ‘๐Ÿคฉ๐ŸŒธ๐Ÿฅฐ๐ŸŽ‰

  8. Hey, Amoeba Sisters (or anyone who can help me)!
    Since human body features, such as eye colour are given depending on the dominant and recessive traits your own parents have, then how can a parent with brown eyes and a parent with green eyes give birth to a child with blue eyes?
    Also, I freaking love the โ€œParamecium Parlorโ€ and โ€œAmoeba Sisters Sisterhoodโ€ cรณmics you guys have in WEBTOON ๐Ÿ˜‰

  9. Hi Amoeba Sisters! My name is Beata (Bee-ah tah) Yacura. I just want to let you know that I am a huge fan! I have autism! If you donโ€™t know what autism is, I can explain it to you. It is a genetic disorder. Autism is when people who canโ€™t socialize. But whatโ€™s beneficial about is they can be fixated on something! I am similar to you Pinky, I am fixated on science. I am always staying curious! When I grow up, I am going to be a scientist. I want to cure diseases for you Pinky, and Petunia!:)

  10. Can you guys make a video about functional groups? And talk about chemical formula and structural formula? Biology has been killing me๐Ÿ˜‚

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  12. YOU CLEVER AMOEBAS
    I'm doing the handout for class, got stuck on understanding what question 13 wants, then went for the answer key, so I can understand the question( I'm good on the rest of it). You CHILDPROOFED it with TWO DOLLARS!!!
    NOOOOOOOOO

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